The change of Psa and Ppa was observed during injection of 5-HT into the lateral ventricle of brain or the auricular vein of anesthetized rabbits. Increase of Ppa and decrease of Psa were found after injection through auricular vein. On the contrary, while 5-HT was injected into lateral ventricule there were increased of Psa and decreased of Ppa. The responses of Ppa induced by 5-HT injecting into lateral ventricle might be related to the transmission of vagus and the action of Ach. The opiumnoid substances might take part in the change of Ppa and Psa while 5-HT was injected into lateral ventricle of brain.

The effects of injecting nitrendipine into lateral cerebroventricle (LCV) andauricular vein (AV) on Ppa and Psa in normal and hypoxic rabbits were observed. Afterinjecting, the Ppa increased 0.22?0.13 kPa and 0.28?0.24 kPa in normal, and 0.06?0.19 kPa and 0.14 ?0.09 kPa in hypoxia respectively. The variation of Ppa after injec-ting LCV reduced markedly (p